This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. To obtain important reproductive data on endangered primates under field conditions.[unreadable] [unreadable] For the muriqui (Brachyteles hypoxanthus), Strier and Ziegler examined the timing of the breeding season with [unreadable] respect to the onset of ovarian cycling. We found that early conception was related to the amount of androgen and [unreadable] estradiol levels. Early conception was associated with lower androgen levels and higher estradiol levels then in [unreadable] females who did not conceive. Fedigan and Ziegler found for the white-faced capuchin (Cebus capucinus), there is [unreadable] a lack of overt signs of ovulation. A means to determine the timing of ovulation is limited. Behavioral observations [unreadable] on the males in the groups indicated that the best indicator of ovarian state was the two-fold increase in male [unreadable] affiliative and sexual behaviors during the conceptive phase. Gould and Ziegler found that for the prosimian, Lemur [unreadable] catta, or the ringtailed lemur that males who live in groups with fewer males show lower cortisol levels and [unreadable] aggression than males who live with a higher density. However, during breeding season competition, male ring [unreadable] tailed lemurs do not show significantly higher levels of cortisol. These studies indicate the type of endocrine data [unreadable] that can be obtained from nonhuman primates under totally free conditions. This research used WNPRC Assay [unreadable] Services. Note: Brachyteles hypoxanthus is not included on NCRR APR system species list. The investigators [unreadable] studied muriquis in addition to white-faced, or white-throated capuchins. This work used private foundation [unreadable] support, mentioned in previous progress reports, and also relied on WNRPC Assay Services.